HVAC Tips: Maintain the Best Humidity Levels (2025)

What Is Humidity?

Humidity is a measure of how much moisture is in air. Too little humidity means that air feels too dry to breathe; too much makes you feel sticky or smothered. If there's not enough humidity, it's easy to overheat; if there's too much, condensation can form on windows, making them foggy. How do you strike a balance? There are ways to control humidity levels inside your home.

What’s the Ideal Indoor Humidity Level?

Most people don’t give humidity levels much thought — it’s a given that indoor humidity levels are influenced by your HVAC system. But what do you really know about humidity?

The average healthy indoor humidity level in winter is 45 percent, while it rises to 55 percent in summer.

There are a few simple guidelines to follow when setting indoor humidity levels: If you have an older heating system, keep it below 50 percent to prevent mold from forming. Because dry air can aggravate allergies and asthma, keep it between 40 percent and 60 percent if there is someone in your household with respiratory concerns. And avoid dropping below 30 percent humidity; drier air can irritate your eyes and nose, and make delicate skin crack.

How Do I Monitor Indoor Humidity Level?

You’ll need to know what humidity levels are inside your home so you can control humidity to feel comfortable. Here are some ways to monitor indoor humidity levels.

• Many electronic thermostats such as the Nest® thermostat provide with an indoor humidity reading. Use your electronic thermostat to monitor humidity inside your home.

• Most humidifiers give you a humidity level reading. Take a look at the reading on your humidifier to find the humidity level inside your home.

• You can buy a humidity monitor to keep track of humidity inside your home. Accurate humidity monitors are relatively inexpensive and can help you quickly see humidity levels inside your home.

How Do I Control Indoor Humidity During Winter?

As your furnace heats indoor air, it expands and becomes dry. To keep indoor air comfortable during winter, you’ll need to humidify air.

Your HVAC system may have a built-in whole house humidifier or you may use portable humidifiers to control indoor humidity during winter.

Here are some tips to control indoor humidity depending on the type of humidifier(s) you use.

Built-in Whole House Humidifier

If your furnace has a built-in, whole house humidifier, follow these tips to ensure it maintains proper humidity levels to keep you comfortable during winter.

• Monitor indoor humidity during winter and adjust your humidifier setting when it’s too dry inside your home.

• Follow the maintenance steps in the owner's manual to keep your humidifier and furnace working efficiently.

• Change the furnace air filter regularly to maintain efficient airflow through your humidifier and your house.

• Schedule a service technician to check and maintain your furnace and built-in humidifier each fall. The tech will tune up your furnace to make sure it heats efficiently and circulates air through your home properly. Furthermore, the tech will maintain the humidifier so it helps keep your home comfortable during winter.

• Have a service technician diagnose and repair your furnace or humidifier as soon as you notice a problem with low humidity and/or detect inadequate airflow through your furnace.

Portable Humidifiers

When you use portable humidifiers to keep your home comfortable in winter, follow these steps to help keep them working efficiently.

1. Monitor humidity levels and adjust settings to keep spaces humidified.

2. Keep the water reservoirs filled with water. Use distilled water if required by the models you use.

3. Clean and maintain your humidifiers according to the instructions in their owner’s manuals.

4. Change your furnace air filter regularly to keep air flowing through your home efficiently so humidified air reaches all spaces.

Also, make sure portable humidifiers are large enough to humidify the spaces they’re in. Add humidifiers or use larger ones if necessary to maintain comfortable humidity levels.

How Do I Control Indoor Humidity During Summer?

In hot, humid climates, the AC unit dehumidifies your home as it cools. Here are ways to help your AC keep your home comfortable during summer.

• Keep your thermostat set at a temperature that will cycle the system enough to dehumidify your home during the summer. You can save on energy bills by setting your thermostat high in summer, but you can suffer health problems if the AC doesn’t run long enough to dehumidify your home. Strike an even balance to save on energy while also staying healthy. The exact thermostat setting you choose may vary depending on how hot it is in your area.

• Set up replacement reminders to and change the AC air filter regularly and keep it fresh.

• Have a service technician tune up your AC system every spring so it works efficiently. The technician makes sure that the evaporator is clean and the inside blower fan works properly so the system dehumidifies your home efficiently.

The moment that you detect that your HVAC unit isn’t helping maintain humidity levels in your home properly, schedule a service technician to examine and repair your system.